Cloudy or Turbid Water

There are many factors that may cause cloudy or turbid water. The most common are organic matter, and/or colloidal solids that are too small and too fine to settle out properly. These suspended particles can cause problems with disinfection processes, and also be an indicator of bacterial activity in the water. Turbidity is measured in NTU's, (nephelometric turbidity units). The turbidity of drinking water should always be less than 1 NTU. Most treated city water is less than .2 NTU.

While it is possible to filter water containing colloidal particles, and/or water that has a color to it, generally filtration is the last step in a process of treating this type of water. Since we primarily supply treatment equipment for very small systems, the type of treatment we might recommend is different than what large-scale municipalites use to treat turbidity.

The first step is to inject a flocculant, or coagulant aid, which allows these microscopic suspended particles to lose their positive charge and "floc" together into larger clumps. This is easily done on small scale systems by using a metering pump and injecting 2 -5 ppm of "Cat-Floc" (one of the many types of flocculant aids used for this purpose) into the water as it flows into a holding tank or storage tank. The water is allowed to settle, and is then followed by filtration to remove any suspended floc.

There are many different designs and application criteria that must be considered, including the water chemistry, flow rates, how the water will be disinfected and what types of filtration to use. In some cases additional treatment such as reverse osmosis or other membrane filtration systems are used in conjunction with the polymer injection and settling.

Often the best first step in determining what is causing the cloudiness is to get an accurate water analysis. You can also fill out an online technical request form and one of our water technicians will assist you in trying to identify the cause of the problem and recommend a solution.